1. Field of the Invention
The present invention relates to a method and to a circuit arrangement for the switching of signals which fall into different transmission speed classes within a program-controlled data exchange having connection circuits and/or connection circuit groups to which are connected feed lines which supply the relevant signals and trunk lines which withdraw the relevant signals, and a switching arrangement which receives the signals supplied via the feed lines to the connection circuits or connection circuit groups, which emits the signals to the required trunk lines via the relevant connection circuits and connection circuit groups, and in which switching processes are executed in response to switching requests from the connection circuits or connection circuit groups.
2. Description of the Prior Art
A method and a circuit arrangement of the above-described type are known in the art; in this connection one may refer to the German Pat. No. 25 08 323. In this known process and circuit arrangement, the signals of the transmission speed classes are fed via the same connection circuits and connection circuit groups. However, it has proved that this technique results in the fact that only a relatively low overall switch-through efficiency can be expected in the switching arrangement, i.e. the number of signals which can be switched through in the switching arrangement per time unit without impermissibly high distortion is relatively low.
A method for increasing the switch-through efficiency of a time division multiplex (t.d.m.) switching system having asynchronous switch-through facilities has also already been proposed; in this connection one may refer to the German Application No. 27 14 888.5. In this method, in a synchronously operating data network, the items of communication are transmitted from input circuits to output circuits independently of a synchronizing pulse frame. The communications transmission is dependent upon the existence of channels having differing data transmission speeds which, however, are in a whole-numbered ratio to one another in accordance with CCITT recommendation X.1. In order to increase the switch-through efficiency of the t.d.m. switching system, it is provided that between the network pulse trains of the various speed stages there is carried out a phase shift having an angular degree which is determined by the number of connected speed stages and their relationship to one another. A disadvantage of this known process, however, resides in the fact that the switching arrangement cannot be operated with a standard network pulse train which normally ensures a simple operation of a switching arrangement. Moreover, it has proved that even when this process is employed, the switch-through efficiency achieved in the switching arrangement is not exceptional.